Methods for noise dampening and attenuation of turbine engine

ABSTRACT

A method to attenuate noise associated with operation of a gas turbine engine during a fracturing operation may include connecting an inlet of a first elongated plenum to an exhaust duct of the gas turbine engine. The method further may include connecting a noise attenuator to a distal end of the first elongated plenum. The noise attenuator may include first and second silencer hoods. The method also may include pivoting the first and second silencer hoods from stowed positions to operative positions so that the second silencer hood in combination with the first silencer hood define a second elongated plenum positioned to receive exhaust gas via the first elongated plenum and the exhaust duct. The first elongated plenum and the second elongated plenum may increase an effective length of the exhaust duct and may reduce sound emission associated with operation of the gas turbine engine.

PRIORITY CLAIMS

This application is a continuation of U.S. Non-Provisional applicationSer. No. 17/498,916, filed Oct. 12, 2021, titled “TURBINE ENGINE EXHAUSTDUCT SYSTEM AND METHODS FOR NOISE DAMPENING AND ATTENUATION,” which is acontinuation of U.S. Non-Provisional application Ser. No. 17/182,325,filed Feb. 23, 2021, titled “TURBINE ENGINE EXHAUST DUCT SYSTEM ANDMETHODS FOR NOISE DAMPENING AND ATTENUATION,” which is a continuation ofU.S. Non-Provisional application Ser. No. 16/948,290, filed Sep. 11,2020, titled “TURBINE ENGINE EXHAUST DUCT SYSTEM AND METHODS FOR NOISEDAMPENING AND ATTENUATION,” now U.S. Pat. No. 10,961,914, issued Mar.30, 2021, which claims priority to and the benefit of, U.S. ProvisionalApplication No. 62/704,567, filed May 15, 2020, titled “TURBINE ENGINEEXHAUST DUCT SYSTEM FOR NOISE DAMPENING AND ATTENUATION,” and U.S.Provisional Application No. 62/899,957, filed Sep. 13, 2019, titled“TURBINE ENGINE EXHAUST DUCT SYSTEM FOR NOISE DAMPENING ANDATTENUATION,” the disclosures of which are incorporated herein byreference in their entireties.

TECHNICAL FIELD

In one aspect, the present disclosure relates to noise attenuation anddampening systems and methods for hydraulic fracturing and, inparticular, to systems and methods for dampening and directional controlof exhaust air flow from a gas turbine of a direct drive turbinefracturing system.

BACKGROUND

The present disclosure relates generally to a mobile fracking systemand, more particularly, to a gas turbine-based mobile fracking systemthat may provide mechanical power through gearboxes connected torespective gas turbines and respective mechanically driven fluid pumpsin a fracturing operation (also referable to as “fracking”). Such amobile fracking system may include a plurality of such directly driventurbine (DDT) fracturing units for use in well stimulation and hydraulicfracturing operations. In addition to offering potential efficiencyadvantages compared to diesel fleets or electric fleets, DDT fracturingunits may offer flexibility in operating on a wide variety of fuelcompositions, while also providing improved reliability, lower emissionsand/or smaller foot prints.

In a fracturing operation, a fluid mixture is injected under pressure ata wellbore into a rock formation that bears hydrocarbon to createfractures within a rock. In operation, the pressurized fluid mixture ispressure pumped down to fracture the subsurface geological formation andallows the flow of the hydrocarbon reserves, such as oil and/or gas. Thefluid mixture may include water, various chemical additives, andproppants (e.g., sand, ceramic materials, and the like as will beunderstood by those skilled in the art). For example, and withoutlimitation, the fracturing fluid may comprise a liquid petroleum gas,linear gelled water, gelled water, gelled oil, slick water, slick oil,poly emulsion, foam/emulsion, liquid carbon dioxide (CO₂), nitrogen gas(N₂), and/or binary fluid and acid.

Mechanical power may be generated by the DDT fracturing units and usedto deliver fracturing fluid through mechanically connected fluid pumpsto a wellbore at the fracturing operation site. Surface pumping systemsincluding fluid pumps are utilized to accommodate the various fluids andare typically mobilized at well sites on, for example, skids ortractor-trailers. In one conventional example, dedicated sources ofpower may include gas turbines connected to a source of natural gas thatdrives the respective gas turbine to produce mechanical power that maybe sent to one or more of the surface pumping systems throughmechanically connected gearboxes and/or transmission systems to operatethe fluid pumps at desired speeds.

The fracturing operation site often encompasses a large footprint withthe number of wells or wellheads and supporting components. Thesupporting components take time to be transported and to be setup forutilization at the fracturing operation sites. Due to the large natureof many fracturing operations, there exists a continued challenge toreduce the environmental impact resulting from fracturing operations.Accordingly, there exists a need for methods and systems for reducingthe environmental impact of noise pollution produced by the fracturingoperations.

SUMMARY

As referenced above, a fracturing operation may include a large numberof gas turbines operating substantially concurrently. As a result, anundesirably large amount of noise may be generated by the fracturingoperation.

The present disclosure is generally directed to systems and methods fordampening and directional control of exhaust air flow from a gas turbineof, for example, a direct drive turbine fracturing system. According tosome embodiments, a method to attenuate noise associated with operationof a gas turbine engine during a fracturing operation may includeconnecting an inlet of a first elongated plenum to an exhaust duct ofthe gas turbine engine to receive exhaust gas via the exhaust duct. Themethod further may include connecting a noise attenuator to a distal endof the first elongated plenum. The noise attenuator may include a firstsilencer hood and a second silencer hood. The method also may includepivoting the first silencer hood from a stowed position at leastpartially overlapping the second silencer hood in a stowed position toan operative position. The method further may include pivoting thesecond silencer hood from the stowed position to an operative positionso that the second silencer hood in combination with the first silencerhood define a second elongated plenum positioned to receive exhaust gasvia the first elongated plenum. The first elongated plenum and thesecond elongated plenum may increase an effective length of the exhaustduct and may reduce sound emission associated with operation of the gasturbine engine.

According to some embodiments, a method to operate a mobile fracturingunit including a trailer, a gas turbine engine connected to the trailer,and a fluid pump connected to the gas turbine engine via a gearbox andto the trailer, may include providing a first elongated plenum having aninlet connected to an exhaust duct of the gas turbine engine to receiveexhaust gas via the exhaust duct during operation of the gas turbineengine. The method further may include providing a noise attenuatorconnected to a distal end of the first elongated plenum. The noiseattenuator may include a first silencer hood and a second silencer hood.The method also may include positioning the first silencer hood from astowed position to an operative position, and positioning the secondsilencer hood from a stowed position to an operative position so thatthe second silencer hood in combination with the first silencer hooddefine a second elongated plenum positioned to receive exhaust gas viathe first elongated plenum. The method further may include operating thegas turbine engine, such that exhaust gas from operation of the gasturbine engine flows from the exhaust duct through the first elongatedplenum and the second elongated plenum to reduce sound emissionassociated with operation of the gas turbine engine.

According to some embodiments, a method to transport from a firstfracturing operation site to a second fracturing operation site a mobilefracturing unit including a trailer, a gas turbine engine connected tothe trailer, and a fluid pump connected to the gas turbine engine via agearbox and to the trailer, may include providing a first elongatedplenum having an inlet connected to an exhaust duct of the gas turbineengine to receive exhaust gas via the exhaust duct during operation ofthe gas turbine engine. The method further may include providing a noiseattenuator connected to a distal end of the first elongated plenum. Thenoise attenuator may include a first silencer hood and a second silencerhood, the first silencer hood in an operative position in combinationwith the second silencer hood in an operative position defining a secondelongated plenum positioned to receive exhaust gas via the firstelongated plenum. The method also may include positioning the firstsilencer hood from the operative position to a stowed position fortransport and positioning the second silencer hood from the operativeposition to a stowed position for transport. The method further mayinclude moving the mobile fracturing unit from the first fracturingoperation site to the second fracturing operation site.

Still other aspects, embodiments, and advantages of these exemplaryaspects and embodiments, are discussed in detail below. Moreover, it isto be understood that both the foregoing information and the followingdetailed description are merely illustrative examples of various aspectsand embodiments, and are intended to provide an overview or frameworkfor understanding the nature and character of the claimed aspects andembodiments. Accordingly, these and other objects, along with advantagesand features of the present disclosure herein disclosed, will becomeapparent through reference to the following description and theaccompanying drawings. Furthermore, it is to be understood that thefeatures of the various embodiments described herein are not mutuallyexclusive and may exist in various combinations and permutations.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the embodiments of the present disclosure, areincorporated in and constitute a part of this specification, illustrateembodiments of the present disclosure, and together with the detaileddescription, serve to explain the principles of the embodimentsdiscussed herein. No attempt is made to show structural details of thisdisclosure in more detail than may be necessary for a fundamentalunderstanding of the exemplary embodiments discussed herein and thevarious ways in which they may be practiced. According to commonpractice, the various features of the drawings discussed below are notnecessarily drawn to scale. Dimensions of various features and elementsin the drawings may be expanded or reduced to more clearly illustratethe embodiments of the disclosure.

FIG. 1 is a schematic top view of an example of a mobile fracking systemshowing an example directly driven turbine fracturing unit having a gasturbine housed inside a trailer in an interior space within the trailerand showing a gearbox connected to the gas turbine for mechanicallytranslating mechanical energy produced by the gas turbine to at leastone fluid pump via a gearbox according to an embodiment of thedisclosure.

FIG. 2 illustrates an example exhaust attenuation system configured toreceive exhaust gas from a gas turbine, the exhaust attenuation systemincluding a lower elongated plenum configured to receive exhaust gasfrom the gas turbine and an upper noise attenuation system that ismovably connected relative to the distal end of the lower elongatedplenum, the upper noise attenuation system being shown in the extendedoperative position according to an embodiment of the disclosure.

FIG. 3 illustrates an example exhaust attenuation system configured toreceive exhaust gas from a gas turbine, the exhaust attenuation systemincluding a lower elongated plenum configured to receive exhaust gasfrom the gas turbine and an upper noise attenuation system that ismovably connected relative to the distal end of the lower elongatedplenum, the upper noise attenuation system being shown in the stowedposition according to an embodiment of the disclosure.

FIG. 4 shows an example exhaust attenuation system illustrating an uppernoise attenuation system having a pair of opposed silencer hoods thatare configured to be hingeably mounted to portions of the distal end ofthe lower elongated plenum and that are independently movable relativeto each other according to an embodiment of the disclosure.

FIG. 5 shows an example lower silencer hood being moved to the operativeposition and shows an example upper silencer hood positioned in theoperative position according to an embodiment of the disclosure.

FIGS. 6A and 6B respectively show a perspective view and an enlargedperspective view of an example retention brace system having a firstpair of opposing retention braces comprising a first brace mounted toexterior portions of the distal end of the lower elongated plenum and asecond brace mounted to an opposed exterior portions of the distal endof the lower elongated plenum, each brace defining a slot that is sizedand shaped for receipt of portions of respective side surfaces of thepair of silencer hoods according to an embodiment of the disclosure.

FIG. 7 shows an example retention brace system according to anembodiment of the disclosure having a first pair of opposing retentionbraces comprising a first brace mounted to exterior portions of thedistal end of the lower elongated plenum and a second brace mounted toan opposed exterior portions of the distal end of the lower elongatedplenum, each brace defining a slot that is sized and shaped for receiptof portions of respective side surfaces of the pair of silencer hoodsand a second pair of opposing retention braces comprising a third bracespaced proximally from the first brace and mounted to exterior portionsthe lower elongated plenum and a fourth brace spaced proximally from thefirst brace and mounted to an opposed exterior portions of the lowerelongated plenum, each brace defining a slot that is sized and shapedfor receipt of respective side surfaces of the pair of silencer hoodswhen the pair of silencer hoods is positioned in the stowed position.

FIG. 8 shows an example upper noise attenuation system having anelongated conduit that has an exterior that is shaped and sized forcomplementary receipt therein the distal portion of the lower elongatedplenum and showing the elongated conduit in the stored positionaccording to an embodiment of the disclosure.

FIG. 9 shows an example upper noise attenuation system having anelongated conduit that has an exterior that is shaped and sized forcomplementary receipt therein the distal portion of the lower elongatedplenum and showing the elongated conduit in the operative positionaccording to an embodiment of the disclosure.

FIG. 10 shows an example guide mounted to an exterior surface of thelower elongated plenum, a rod configured for operative slideable receipttherein the slot of the guide, and means for selective axial movement ofthe rod for movement of the elongated conduit between the stowedposition and the operative position according to an embodiment of thedisclosure.

FIG. 11 schematically illustrates portions of a means for selectiveaxial movement of the rod for movement of the elongated conduit betweenthe stowed position and the operative position according to anembodiment of the disclosure.

DETAILED DESCRIPTION

Referring now to the drawings in which like numerals indicate like partsthroughout the several views, the following description is provided asan enabling teaching of exemplary embodiments, and those skilled in therelevant art will recognize that many changes may be made to theembodiments described. It also will be apparent that some of the desiredbenefits of the embodiments described may be obtained by selecting someof the features of the embodiments without utilizing other features.Accordingly, those skilled in the art will recognize that manymodifications and adaptations to the embodiments described are possibleand may even be desirable in certain circumstances, and are a part ofthe disclosure. Thus, the following description is provided asillustrative of the principles of the embodiments and not in limitationthereof.

The phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. As used herein, theterm “plurality” refers to two or more items or components. The terms“comprising,” “including,” “carrying,” “having,” “containing,” and“involving,” whether in the written description or the claims and thelike, are open-ended terms, i.e., to mean “including but not limitedto.” Thus, the use of such terms is meant to encompass the items listedthereafter, and equivalents thereof, as well as additional items. Onlythe transitional phrases “consisting of” and “consisting essentiallyof,” are closed or semi-closed transitional phrases, respectively, withrespect to any claims. Use of ordinal terms such as “first,” “second,”“third,” and the like in the claims to modify a claim element does notby itself connote any priority, precedence, or order of one claimelement over another or the temporal order in which acts of a method areperformed, but are used merely as labels to distinguish one claimelement having a certain name from another element having a same name(but for use of the ordinal term) to distinguish claim elements.

As used herein, the term “trailer” refers to any transportationassembly, including, but not limited to, a transport, truck, skid,and/or barge used to transport relatively heavy structures, such asfracturing equipment.

As used herein, the term “directly driven turbine” DDT refers to boththe gas turbine and the mechanical energy transport sections of adirectly driven turbine fracturing unit. The gas turbine receiveshydrocarbon fuel, such as natural gas, and converts the hydrocarbon fuelinto mechanical energy that is mechanically transferred via a gearbox toat least one fluid pump. It is further contemplated that a gas turbineas described herein may be a gas fueled turbine, a dual-fuel turbine,and the like.

In one embodiment, a mobile fracking system 10 may include a trailer 12,a gas turbine 14, and an exhaust attenuation system 20 configured toreceive exhaust gas from the gas turbine. FIG. 1 is a schematic diagramof an embodiment of a mobile fracking system 10 showing the trailer 12having a rear end, a front end, a bottom end, and a top end that definesan interior space. As shown, the gas turbine 14 is housed inside thetrailer in the interior space. To improve mobility over a variety ofroadways, the trailer may have a maximum height, a maximum width, and amaximum length that would be suitable for passage on conventional roadsand expressways. Further, the trailer may comprise at least three axlesused to support and distribute the weight on trailer. Other embodimentsof the trailer may exceed three axles depending on the total transportweight and it is contemplated that the dimensions and the number ofaxles may be adjusted to allow for the transport over roadways thattypically mandate certain height, length, and weight restrictions.

The trailer 12 may house at least one or more of the followingequipment: (1) an inlet plenum; (2) the gas turbine 14; (3) the exhaustattenuation system 20 to remove exhaust gas from gas turbine into theatmosphere, (4) a gearbox and/or transmission 16 connected to a rotaryoutput of the gas turbine, and (5) a fluid pump 18 operatively connectedto the output of the gearbox. Other components not shown in FIG. 1, butwhich may also be located on the trailer include a control system, aturbine lube oil system, and a fire suppression system. The turbine lubeoil system may be configured to selectively operate turbine lube oilfiltering and cooling systems. In one embodiment, the fire suppressionsystem may also comprise sprinklers, water mist, clean agent, foamsprinkler, carbon dioxide, and/or other equipment used to suppress afire or provide fire protection for the gas turbine. Mounting of theturbine lube oil systems and the fire suppression system onto the DDTfracturing unit reduces trailer operative footprint by eliminating theneed for an auxiliary transport and connections for the turbine andgenerator lube oil, filtering, cooling systems and the fire suppressionsystem to the gas turbine generator transport.

One skilled in the art will appreciate that the gas turbine 14 may beconfigured to generate mechanical energy (i.e., rotation of a shaft)from a hydrocarbon fuel source, such as natural gas, liquefied naturalgas, condensate, and/or other liquid fuels. As schematicallyillustrated, the gas turbine shaft is connected to the gearbox such thatthe gearbox converts the supplied mechanical energy from the rotation ofthe gas turbine shaft to a downstream shaft assembly that is rotated ata desired speed and torque to the downstream mechanically connectedfluid pump. The gas turbine may be a gas turbine, such as the GE familyof gas turbines, the Pratt and Whitney family of gas turbines, or anyother gas turbine and/or dual-fuel turbine that generates sufficientmechanical power for the production of the desired level of brakehorsepower to the downstream fluid pump for fracking operations at oneor more well sites.

The trailer 12 may also comprise gas turbine inlet filter(s) configuredto provide ventilation air and combustion air via one or more inletplenums (not shown) to the gas turbine. Additionally, enclosureventilation inlets may be added to increase the amount of ventilationair, which may be used to cool the gas turbine and ventilate the gasturbine enclosure. The combustion air may be the air that is supplied tothe gas turbine to aid in the production of mechanical energy. The inletplenum may be configured to collect the intake air from the gas turbineinlet filter and supply the intake air to the gas turbine.

In one embodiment and referring to FIGS. 2-11, the exhaust attenuationsystem 20 may be attached to a portion of the trailer and may include alower elongated plenum 30 and an upper noise attenuation system 40 thatis movably connected relative to the distal end of the lower elongatedplenum. The lower elongated plenum 30 has a proximal end and a distalend and extends a first distance between the respective proximal anddistal ends. The lower elongated plenum 30 defines an inlet 32 adjacentthe proximal end of the lower elongated plenum 30 that is configured toreceive exhaust gas from the gas turbine. In one aspect, the lowerelongated plenum extends longitudinally away from a bottom surface ofthe trailer about an exhaust axis. The exhaust axis may be positioned atan angle relative to the bottom surface and, in one non-limitingexample, may be substantially normal to the bottom surface,substantially vertical, and/or substantially upright.

It is contemplated that the exhaust attenuation system 20 will beconstructed of materials that are capable of withstanding extremetemperatures, such as for example and without limitation, to about 1250°F. (676° C.), that are associated with exhaust gases exiting gasturbines.

In embodiments, the upper noise attenuation system 40 may be configuredto be selectively movable between a stowed position and an operative,upright, position. In the stowed position, an outlet end portion 42 ofthe upper noise attenuation system is positioned proximate to the distalend of the lower elongated plenum, and, in the operative position, theupper noise attenuation system defines an upper elongated plenum 50 thatis in fluid communication with the distal end of the lower elongatedplenum. In this operative position, an outlet 52 of the upper noiseelongated plenum is spaced away from the distal end of the lowerelongated plenum at a second distance that is greater than the firstdistance. Further, it is contemplated that the upper noise attenuationsystem, in the operative position, may extend longitudinally away fromthe distal end of the lower elongated plenum about the exhaust axis.

The mobile fracking system affects a reduction in sound emission byincreasing the effective length of the gas turbine exhaust stack.Attenuation of rectangular duct in the 63 Hz to 250 Hz octave frequencybands may be expressed as:

$\begin{matrix}{{\Delta\; L_{duct}} = {17.0\left( \frac{P}{S} \right)^{- {.025}}f^{- 0.85}l}} & (1) \\{{\Delta\; L_{duct}} = {1.64\left( \frac{P}{S} \right)^{- 0.73}f^{- 0.58}l}} & (2)\end{matrix}$

TABLE 1 Exhaust attenuation with unlined rectangular duct Exhaust Ductwith Proposed System Exhaust Reference Exhaust Duct ΔL_(duct, N) − PWL fΔL_(duct, O) PWL ΔL_(duct, N) ΔL_(duct, O) PWL dB Hz dB dB dB dB dB120.0 63.5 2.90 116.1 4.06 1.16 114.9 129.0 125 1.96 127.0 2.74 0.78126.2 127.0 250 1.31 125.7 1.83 0.52 125.2 127.0 500 0.88 126.1 1.230.35 125.8 126.0 1000 0.59 125.4 0.82 0.23 125.2 130.0 2000 0.39 129.60.55 0.16 129.4

For example, and without limitation, and taken from Table 1 above,proposed exhaust system may affect a 40% increase in sound attenuationand a maximum in 1.2 dB in sound pressure by selective operativeincrease in the elongate length of the exhaust plenum from 16.1 ft. to22.6 ft.

In embodiments, the mobile fracking system 10 may include a first plenum22 configured to receive exhaust gas from the gas turbine. In thisaspect, a first end of the first plenum is connected to, and in fluidcommunication with, an exhaust outlet of the gas turbine and a secondend of the first plenum connected to, and in fluid communication with,the inlet of the lower elongated plenum. For example, the gas turbinemay be mounted to or otherwise supported thereon the bottom surface ofthe trailer and the first plenum may extend longitudinally substantiallyparallel to the bottom surface.

Optionally, the upper noise attenuation system 40 may include at leastone array of baffles 70 that are configured to attenuate noise. Thearray of baffles 70 may include a plurality of baffles 72 that aredistributed parallel to a common axis and that define a plurality ofslots 74 defined by and between the plurality of baffles. In oneexemplary aspect, the at least one array of baffles 70 may be mountedtherein a portion of the upper elongated plenum in communication withthe exhaust gas passing therethrough the upper elongated plenum to theoutlet to supplement the noise dampening capabilities of the noiseattenuation system.

In embodiments and referring to FIGS. 2-7, the upper noise attenuationsystem 40 may include a pair of opposed and cooperating silencer hoods46. In this aspect, each silencer hood 46 may have a planer surface 48having opposed side edges 50 and a pair of opposing side surfaces 52that extend outwardly from portions of the respective side edges of theplaner surface. Each silencer hood 46 may be configured to be hingeablymounted to portions of a distal end of the lower elongated plenum suchthat, in the operative position, the pair of opposed silencer hoods arepositioned substantially upright so that the planer surfaces of therespective back edges are in parallel opposition and that the respectiveside surface are also in parallel opposition to form the elongated upperelongated plenum.

As exemplarily shown in the figures, the pair of opposed silencer hoods46 may include an upper silencer hood 54 and a lower silencer hood 56that are configured to cooperatively slideably engage relative to eachother when moving therebetween the stowed position and the operativeposition. In this example, the respective opposed upper and lowersilencer hoods may be opened in a sequential manner. First, the uppersilencer hood may be raised independently from the lower silencer hood.As shown, an anchor point mounted on a back surface of the planarsurface of the upper silencer hood proximate a bottom edge of the backsurface may be connected to a wire that is operative connected to aspooling system that is configured for selective movement of theconnected silencer hood between the stowed and operative positions. Inoperation, the spooling system is operated to open or otherwise urge theupper silencer hood to the operative position and may comprise a winch,such as, for example and without limitation, an electric winch, ahydraulic winch, a pneumatic winch, and the like. It is contemplatedthat, once the upper silencer hood is in the operative position, tensionmay be maintained on the wire to aid in maintaining the upper silencerhood in the operative position until the upper silencer hood is loweredto the stowed position for transport. Optionally, a mechanical limitswitch on the spooling system that may be configured to determinedistance the wire is required to move to open and close the respectivesilencer hoods 46.

Similarly, the lower silencer hood 56 may be raised independently fromthe upper silencer hood 54. As shown, an anchor point mounted on a backsurface of the planar surface of the lower silencer hood proximate abottom edge of the back surface may be connected to a wire that isoperative connected to the spooling system. In operation, after theupper silencer hood is positioned in the operative position, thespooling system of the lower silencer hood may be operated to open orotherwise urge the lower silencer hood to the operative position. It iscontemplated that, once the lower silencer hood is in the operativeposition, tension may be maintained on the wire to aid in maintainingthe lower silencer hood in the operative position until the lowersilencer hood is lowered to the stowed position for transport. In thisexample, the lower silencer hood would be lowered first in sequence whenthe respective opposed upper and lower silencer hoods are closed orotherwise moved to the stowed position.

As noted above, the respective upper and lower silencer hoods 54, 56 maybe maneuvered to and about the operative and the stowed positionsthrough the use of one or more actuators, such as linear actuatorsand/or rotary actuators, and in some embodiments, one or more cablesand/or one or more mechanical linkages. In some embodiments, the one ormore actuators may be electrically-actuated, pneumatically-actuated,and/or hydraulically-actuated (e.g., via hydraulic cylinders and/orhydraulic motors). For example, the respective upper and lower silencerhoods 54, 56 may be maneuvered to and about the operative and the stowedpositions through the use of a spooling system comprising electrical,mechanical, and/or pneumatic winches that contain spooled wire that areconnected to the anchor points strategically positioned on therespective upper and lower silencer hoods 54, 56.

Optionally, the exhaust attenuation system shown in FIGS. 2-5, 6A, 6B,and 7 may further include a retention brace system 90. In this aspect,the retention brace system may include a first pair of opposingretention braces 92 and a second pair of opposing retention braces 99.The first pair of opposing retention braces 92 may include a first brace93 mounted to exterior portions of the distal end of the lower elongatedplenum and a second brace 94 mounted to an opposed exterior portions ofthe distal end of the lower elongated plenum. Each brace of the firstpair of opposing retention braces includes a bar 95 that extends betweena first end mount 96 and an opposing second end mount 97 such that, whenthe respective first and second end mounts are positioned therein thelower elongated plenum, the bar is spaced from an exterior surface ofthe distal end of the lower elongated plenum and defines a slot 98 thatis sized and shaped for receipt of portions of respective side surfacesof the pair of silencer hoods.

Similarly, the second pair of opposing retention braces 99 includes athird brace 100 spaced proximally from the first brace and mounted toexterior portions the lower elongated plenum and a fourth brace 102spaced proximally from the first brace and mounted to an opposedexterior portions of the lower elongated plenum. In this aspect, eachbrace of the second pair of opposing retention braces includes a bar 95extending between a first end mount 96 and an opposing second end mount97 such that, when the respective first and second end mounts arepositioned therein the lower elongated plenum, the bar is spaced from anexterior surface of the lower elongated plenum and defines a slot 98that is sized and shaped for receipt of respective side surfaces of thepair of silencer hoods when the pair of silencer hoods is positioned inthe stowed position.

In embodiments, the upper noise attenuation system 40 may include atleast one array of baffles configured to attenuate noise that is mountedtherein at least a portion of the planer surface of at least one or ineach of the opposed silencer hoods.

In other embodiments and referring to FIGS. 8-11, the upper noiseattenuation system 40 may optionally include an elongated conduit 110that has an exterior surface shape that is shaped and sized forcomplementary receipt therein a distal portion of the lower elongatedplenum 30. In this aspect, in the stowed position, the elongated conduit110 is positioned substantially therein the lower elongated plenum suchthat an outlet end 112 of the elongated conduit is positioned proximateto the distal end of the lower elongated plenum. In the operativeposition, the elongated conduit 110 is selectively movable about andalong an about an exhaust axis outwardly away from the distal end of thelower elongated plenum such that a proximal end 114 of the elongatedconduit is positioned proximate the distal end of the lower elongatedplenum and the outlet end 112 of the elongated conduit forms the outletof the upper elongated plenum.

In this aspect, to operatively move or otherwise urge the elongatedconduit 110 about and between the stowed and operative positions, theupper noise attenuation system 40 may include at least one guide 120mounted to an exterior surface (e.g., at an upper end thereof) of thelower elongated plenum 30. As will be appreciated, the guide 120 maydefine an elongated enclosed slot extending parallel to the exhaustaxis. A rod 122 having a distal end mounted to an outermost edge surfaceof the outlet end 112 of the elongated conduit 110 may be provided thatis configured for operative slideably receipt therein the slot of theguide 120. To operatively move the rod 122 and thereby move theelongated conduit 110 relative to the lower elongated plenum 30, a meansfor selective axial movement of the rod 122 and thus for movement of theelongated conduit 110 may be provided for selective movement of theelongated conduit 110 between the stowed position (see, e.g., FIGS. 8and 10) and the operative position (see, e.g., FIG. 9).

As illustrated in FIGS. 8-11, selective axial movement of the rod 122may be provided by an extension assembly 124. In some examples, theextension assembly 124 may include pairs of pulleys 126 connected toopposing sides 128 of the lower elongated plenum 30, and a drive shaft130 coupled to the lower elongated plenum 30. The extension assembly 124may also include a pair of cables 132, each of which is anchored to alower end of the lower elongated plenum 30. A pair of drive wheels 134may be connected to each end of the drive shaft 130, and each of thedrive wheels 134 may be configured to retract or extend a respective oneof the pair of cables 132, for example, such that retraction of the pairof cables 132 causes the rod 122 to push the elongated conduit 110 toextend from the lower elongated plenum 30 and into the operativeposition (see FIG. 9), and extension of the pair of cables 132 causesthe rod 122 to return to a lowered position, thereby allowing theelongated conduit 110 to return to the stowed position (see FIGS. 8 and10). In some examples, at ends of the respective rods 122 remote fromthe outlet end 112 of the elongated conduit 110, a rod pulley 136 may beprovided for engaging a respective cable 132 to facilitate movement ofthe elongated conduit 110 relative to the lower elongated plenum 30. Asshown in FIG. 11, in some examples, a drive gear 138 may be connected tothe drive shaft 130 to facilitate rotation of the drive shaft 130 via anactuator including a mating gear, such as a linear actuator and/or arotary actuator, for example, a gear shaft and a prime mover such as,for example, and without limitation, a winch. As one skilled in the artwill appreciate, when such a prime mover is activated, the illustrateddrive gear 138 of the drive shaft 130 rotates, which causes thecomplementary rotation of the drive wheels 134 connected to therespective ends of the drive shaft 130. In turn, the cables 132 willspool onto each of the drive wheels 134 and via the pulleys 126, willaffect the translation of the proximal end of the respective rods 122 toextend the elongated conduit 110 into the operative position.

In this embodiment, the upper noise attenuation system may include atleast one array of baffles configured to attenuate noise that may bemounted therein an outlet end of the elongated conduit.

It is contemplated that the means for selective axial movement of therod for selective movement of the elongated conduit 110 between thestowed position and the operative position of the elongated conduit 110may comprise one or more actuators, such as linear actuators and/orrotary actuators, and in some embodiments, one or more cables and/or oneor more mechanical linkages. In some embodiments, the one or moreactuators may be electrically-actuated, pneumatically-actuated, and/orhydraulically-actuated (e.g., via hydraulic cylinders and/or hydraulicmotors). For example, selective movement of the elongated conduit 110between the stowed position and the operative position of the elongatedconduit 110 may be provided by the spooling system described above. Inthis aspect, the spooling system may comprise electrical, mechanical,and/or pneumatic winches that contain spooled wire and that areconfigured to spool wire onto each drum via the pulleys to affect theaxial movement of the rod.

Optionally, the exhaust attenuation system 20 may further comprise asupervisory control system that is configured to utilize a series ofdigital input and output signals that will result in the controlledoperation of the upper noise attenuation system 40. In this aspect, theexhaust attenuation system 20 may comprise a plurality of positionalfeedback sensors in communication with the supervisory control system.The positional feedback sensors are operatively mounted to respectiveportions of the upper noise attenuation system 40 such that the sensorsmay actuate when the upper noise attenuation system 40 is positioned inthe stowed position and when in the operative, upright, position.

Each positional feedback sensor may comprise, for example and withoutlimitation, a digital proximity switch that is configured to actuatewhen the positional feedback sensor's electromagnetic detection fieldcomes in contact with a portion of the metallic surface of the exhauststack. Upon actuation, each digital proximity switch is configured tosend a digital signal to the supervisory control system indicative ofthe position of the respective upper and lower silencer hoods 54, 56 or,optionally, the respective position of the elongated conduit 110relative to the distal end of the lower elongated plenum.

Optionally, it is contemplated that the positional feedback sensor maybe an analog position sensor that is configured to provide positionalfeedback to the supervisory control system of the positions of therespective upper and lower silencer hoods 54, 56 or, optionally, therespective position of the elongated conduit 110 relative to the distalend of the lower elongated plenum. In this exemplary aspect, the analogposition sensor may be configured to transmit a scaled current orvoltage signal that depending on the value allows the control system toidentify the accurate position of the upper noise attenuation system 40.An exemplary analog position sensor, such as a Sick absolute encoder,models AFS/AFM60 SSI, would be suitable for this application.

The positional feedback sensors allow the operator to know the positionof the respective upper and lower silencer hoods 54, 56 or, optionally,the respective position of the elongated conduit 110 relative to thedistal end of the lower elongated plenum and to further allow for theprotection of equipment on the gas turbine skid. For example, thesupervisory control system may generate an interlock signal that wouldprohibit the ignition of the gas turbine engine upon receipt of a signalfrom the respective positional feedback sensors that indicates that theupper noise attenuation system 40 is in the closed position. Thus, theinterlock signal preventing turbine operation into a sealed cavityprevents the possibility of serious damage to the turbine engine due toundesired backpressure.

In operational aspects, it is contemplated that the upper noiseattenuation system 40 may be actuated to move between the stowed andoperative positions by manual operation of a physical lever. In thisaspect, and if the spooling system includes a pneumatic winch, theselective actuation of the manual level may allow for the flow of air tothe pneumatic motor resulting in rotary motion at the winch. Optionally,if the spooling system includes a hydraulic winch, the selectiveactuation of the manual level may allow for the flow of hydraulic oilinto the stator of the hydraulic motor to produce the desired rotarymotion and torque to actuate the upper noise attenuation system 40. In afurther, exemplary aspect, if the spooling system includes an electricalwinch, a switching device may be provided that is configured to allowfor the selective application of current to the electric winch motor.The switching device may exemplarily be in the form of a toggle switchthat allows the electrical circuit to the motor to be completed uponactuation such that the electric motor performs the desired rotarymotion.

In a further optional aspect, the supervisory control system of theexhaust attenuation system 20 may comprise a SCADA (supervisory controland data acquisition) system. Exemplarily, if pneumatic and/or hydraulicwinches are used, a directional control valve with an electrical coilmay be positioned between the respective pressurized sources of air oroil and the downstream pneumatic or hydraulic motors. Operationally, anoperation signal transmitted or outputted to the directional controlvalve from the SCADA system upon operator input. In this aspect, theoperation signal could be a PWM signal with reverse polarity. Forexample, when the operator pushes an input on a human machine interface,which is identified by the programmable logistical controller, and thenecessary output operation signal is sent to the directional controlvalve that allows for proportional flow of the required air or oil mediato the winch motor. Optionally, this methodology may also be used for anelectrical winch but, in this aspect, the output operation signal wouldenergize a relay that allows for low voltage, high current power toreach the electrical motor and perform the proportional operationfunction. It is contemplated that these actuation functions may be madefully autonomous by implementing a start-up sequence such that, when theoperator selects to start the unit, a series of sequenced signal outputsare driven around the frac pump trailer that will verify that theexhaust attenuation system 20 is in the open, operative position, theauxiliary power is verified to be on line, the necessary safety andcommunication checks performed, and then the gas turbine is allowed tostart. In this exemplary aspect, a single input to actuate the exhaustattenuation system 20 to move to the open, operative position mayinitiate the issuance of a series of outputs from the SCADA system,which may save the operator time and may reduce complexity of how toindividually perform these sequential outputs.

This application is a continuation of U.S. Non-Provisional applicationSer. No. 17/498,916, filed Oct. 12, 2021, titled “TURBINE ENGINE EXHAUSTDUCT SYSTEM AND METHODS FOR NOISE DAMPENING AND ATTENUATION,” which is acontinuation of U.S. Non-Provisional application Ser. No. 17/182,325,filed Feb. 23, 2021, titled “TURBINE ENGINE EXHAUST DUCT SYSTEM ANDMETHODS FOR NOISE DAMPENING AND ATTENUATION,” which is a continuation ofU.S. Non-Provisional application Ser. No. 16/948,290, filed Sep. 11,2020, titled “TURBINE ENGINE EXHAUST DUCT SYSTEM AND METHODS FOR NOISEDAMPENING AND ATTENUATION,” now U.S. Pat. No. 10,961,914, issued Mar.30, 2021, which claims priority to and the benefit of, U.S. ProvisionalApplication No. 62/704,567, filed May 15, 2020, titled “TURBINE ENGINEEXHAUST DUCT SYSTEM FOR NOISE DAMPENING AND ATTENUATION,” and U.S.Provisional Application No. 62/899,957, filed Sep. 13, 2019, titled“TURBINE ENGINE EXHAUST DUCT SYSTEM FOR NOISE DAMPENING ANDATTENUATION,” the disclosures of which are incorporated herein byreference in their entireties.

Although only a few exemplary embodiments have been described in detailherein, those skilled in the art will readily appreciate that manymodifications are possible in the exemplary embodiments withoutmaterially departing from the novel teachings and advantages of theembodiments of the present disclosure. Accordingly, all suchmodifications are intended to be included within the scope of theembodiments of the present disclosure as defined in the followingclaims.

What is claimed:
 1. A method to attenuate noise associated withoperation of a gas turbine engine during a fracturing operation, themethod comprising: connecting an inlet of a first elongated plenum to anexhaust duct of the gas turbine engine to receive exhaust gas via theexhaust duct; connecting a noise attenuator to a distal end of the firstelongated plenum, the noise attenuator including a first silencer hoodand a second silencer hood; pivoting the first silencer hood from astowed position at least partially overlapping the second silencer hoodin a stowed position to an operative position; and pivoting the secondsilencer hood from the stowed position to an operative position so thatthe second silencer hood in combination with the first silencer hooddefine a second elongated plenum positioned to receive exhaust gas viathe first elongated plenum, the first elongated plenum and the secondelongated plenum increasing an effective length of the exhaust duct andreducing sound emission associated with operation of the gas turbineengine.
 2. The method of claim 1, wherein: pivoting the first silencerhood from the stowed position to the operative position comprisesactivating a first actuator connected to the first elongated plenum andthe first silencer hood; and pivoting the second silencer hood from thestowed position to the operative position comprises activating a secondactuator connected to the first elongated plenum and the second silencerhood.
 3. The method of claim 2, wherein: activating the first actuatorcomprises activating one or more of a first linear actuator or a firstrotary actuator; and activating the second actuator comprises activatingone or more of a second linear actuator or a second rotary actuator. 4.The method of claim 2, wherein: activating the first actuator comprisesone of electrically activating the first actuator, pneumaticallyactivating the first actuator, or hydraulically activating the firstactuator; and activating the second actuator comprises one ofelectrically activating the second actuator, pneumatically activatingthe second actuator, or hydraulically activating the second actuator. 5.The method of claim 1, wherein: the first silencer hood comprises afirst surface, a first side surface, and a second side surface; thesecond silencer hood comprises a second surface, a third side surface,and a fourth side surface; and pivoting the first silencer hood from thestowed position to the operative position and pivoting the secondsilencer hood from the stowed position to the operative positioncomprises pivoting the first silencer hood and the second silencer hood,such that the first surface and the second surface are in parallelopposition relative to one another, and the first surface, the secondsurface, and two or more of the first side surface, the second sidesurface, the third side surface, or the fourth side surface form thesecond elongated plenum.
 6. The method of claim 5, wherein in the stowedposition, the first surface and the second surface at least partiallyoverlap one another proximate the distal end of the first elongatedplenum.
 7. The method of claim 1, further comprising: receiving, at acontrol system, one or more signals indicative of a position of one ormore of the first silencer hood or the second silencer hood;determining, via the control system, based at least in part on the oneor more signals, the position of one or more of the first silencer hoodor the second silencer hood; and controlling, via the control system,based at least in part on the position of one or more of the firstsilencer hood or the second silencer hood, operation of the gas turbineengine.
 8. The method of claim 7, wherein controlling operation of thegas turbine engine comprises preventing ignition of the gas turbineengine when the one or more signals is indicative of one or more of thefirst silencer hood or the second silencer hood not being in theoperative position to prevent damage to the gas turbine engine.
 9. Amethod to operate a mobile fracturing unit comprising a trailer, a gasturbine engine connected to the trailer, and a fluid pump connected tothe gas turbine engine via a gearbox and to the trailer, the methodcomprising: providing a first elongated plenum having an inlet connectedto an exhaust duct of the gas turbine engine to receive exhaust gas viathe exhaust duct during operation of the gas turbine engine; providing anoise attenuator connected to a distal end of the first elongatedplenum, the noise attenuator including a first silencer hood and asecond silencer hood; positioning the first silencer hood from a stowedposition to an operative position; positioning the second silencer hoodfrom a stowed position to an operative position so that the secondsilencer hood in combination with the first silencer hood define asecond elongated plenum positioned to receive exhaust gas via the firstelongated plenum; and operating the gas turbine engine such that exhaustgas from operation of the gas turbine engine flows from the exhaust ductthrough the first elongated plenum and the second elongated plenum toreduce sound emission associated with operation of the gas turbineengine.
 10. The method of claim 9, further comprising: prior tooperating the gas turbine engine, receiving, at a control system, one ormore signals indicative of a position of one or more of the firstsilencer hood or the second silencer hood; determining, via the controlsystem, based at least in part on the one or more signals, the positionof one or more of the first silencer hood or the second silencer hood;and controlling, via the control system, based at least in part on theposition of one or more of the first silencer hood or the secondsilencer hood, operation of the gas turbine engine.
 11. The method ofclaim 10, wherein controlling operation of the gas turbine enginecomprises preventing ignition of the gas turbine engine when the one ormore signals is indicative of one or more of the first silencer hood orthe second silencer hood not being in the operative position to preventdamage to the gas turbine engine.
 12. The method of claim 9, whereinpositioning the first silencer hood from the stowed position to theoperative position comprises pivoting the first silencer hood from an atleast partially overlapping position relative to the second silencerhood in the stowed position to the operative position.
 13. The method ofclaim 9, wherein: positioning the first silencer hood from the stowedposition to the operative position comprises activating a first actuatorconnected to the first elongated plenum and the first silencer hood; andpositioning the second silencer hood from the stowed position to theoperative position comprises activating a second actuator connected tothe first elongated plenum and the second silencer hood.
 14. The methodof claim 13, wherein: activating the first actuator comprises activatingone or more of a first linear actuator or a first rotary actuator; andactivating the second actuator comprises activating one or more of asecond linear actuator or a second rotary actuator.
 15. The method ofclaim 13, wherein: activating the first actuator comprises one ofelectrically activating the first actuator, pneumatically activating thefirst actuator, or hydraulically activating the first actuator; andactivating the second actuator comprises one of electrically activatingthe second actuator, pneumatically activating the second actuator, orhydraulically activating the second actuator.
 16. The method of claim 9,wherein: the first silencer hood comprises a first surface, a first sidesurface, and a second side surface; the second silencer hood comprises asecond surface, a third side surface, and a fourth side surface; andpositioning the first silencer hood from the stowed position to theoperative position and positioning the second silencer hood from thestowed position to the operative position comprises pivoting the firstsilencer hood and the second silencer hood, such that the first surfaceand the second surface are in parallel opposition relative to oneanother, and the first surface, the second surface, and two or more ofthe first side surface, the second side surface, the third side surface,or the fourth side surface form the second elongated plenum.
 17. Themethod of claim 16, wherein in the stowed position, the first surfaceand the second surface at least partially overlap one another proximatethe distal end of the first elongated plenum.
 18. A method to transportfrom a first fracturing operation site to a second fracturing operationsite a mobile fracturing unit comprising a trailer, a gas turbine engineconnected to the trailer, and a fluid pump connected to the gas turbineengine via a gearbox and to the trailer, the method comprising:providing a first elongated plenum having an inlet connected to anexhaust duct of the gas turbine engine to receive exhaust gas via theexhaust duct during operation of the gas turbine engine; providing anoise attenuator connected to a distal end of the first elongatedplenum, the noise attenuator including a first silencer hood and asecond silencer hood, the first silencer hood in an operative positionin combination with the second silencer hood in an operative positiondefining a second elongated plenum positioned to receive exhaust gas viathe first elongated plenum; positioning the first silencer hood from theoperative position to a stowed position for transport; positioning thesecond silencer hood from the operative position to a stowed positionfor transport; and moving the mobile fracturing unit from the firstfracturing operation site to the second fracturing operation site. 19.The method of claim 18, wherein positioning the second silencer hoodfrom the operative position to the stowed position comprises pivotingthe second silencer hood to a position in which the second silencer hoodat least partially overlaps the first silencer hood in the stowedposition.
 20. The method of claim 18, wherein positioning the firstsilencer hood from the operative position to the stowed position andpositioning the second silencer hood from the operative position to thestowed position comprises moving the first silencer hood and the secondsilencer hood to a position adjacent the distal end of the firstelongated plenum.
 21. The method of claim 18, further comprising: at thesecond fracturing operation site, pivoting the second silencer hood fromthe stowed position to the operative position; and pivoting the firstsilencer hood from the stowed position to the operative position so thatthe first silencer hood in combination with the second silencer hooddefine the second elongated plenum positioned to receive exhaust gas viathe first elongated plenum.
 22. The method of claim 21, furthercomprising: receiving, at a control system associated with the mobilefracturing unit, one or more signals indicative of a position of one ormore of the first silencer hood or the second silencer hood;determining, via the control system, based at least in part on the oneor more signals, the position of one or more of the first silencer hoodor the second silencer hood; and controlling, via the control system,based at least in part on the position of one or more of the firstsilencer hood or the second silencer hood, operation of the gas turbineengine.
 23. The method of claim 22, wherein controlling operation of thegas turbine engine comprises preventing ignition of the gas turbineengine when the one or more signals is indicative of one or more of thefirst silencer hood or the second silencer hood not being in theoperative position to prevent damage to the gas turbine engine.
 24. Themethod of claim 21, wherein pivoting the second silencer hood from thestowed position to the operative position comprises pivoting the secondsilencer hood from an at least partially overlapping position relativeto the first silencer hood in the stowed position to the operativeposition.
 25. The method of claim 21, wherein: pivoting the firstsilencer hood from the stowed position to the operative positioncomprises activating a first actuator connected to the first elongatedplenum and the first silencer hood; and pivoting the second silencerhood from the stowed position to the operative position comprisesactivating a second actuator connected to the first elongated plenum andthe second silencer hood.
 26. The method of claim 25, wherein:activating the first actuator comprises activating one or more of afirst linear actuator or a first rotary actuator; and activating thesecond actuator comprises activating one or more of a second linearactuator or a second rotary actuator.
 27. The method of claim 25,wherein: activating the first actuator comprises one of electricallyactivating the first actuator, pneumatically activating the firstactuator, or hydraulically activating the first actuator; and activatingthe second actuator comprises one of electrically activating the secondactuator, pneumatically activating the second actuator, or hydraulicallyactivating the second actuator.
 28. The method of claim 21, wherein: thefirst silencer hood comprises a first surface, a first side surface, anda second side surface; the second silencer hood comprises a secondsurface, a third side surface, and a fourth side surface; and pivotingthe first silencer hood from the stowed position to the operativeposition and pivoting the second silencer hood from the stowed positionto the operative position comprises pivoting the first silencer hood andthe second silencer hood, such that the first surface and the secondsurface are in parallel opposition relative to one another, and thefirst surface, the second surface, and two or more of the first sidesurface, the second side surface, the third side surface, or the fourthside surface form the second elongated plenum.
 29. The method of claim28, wherein in the stowed position, the first surface and the secondsurface at least partially overlap one another proximate the distal endof the first elongated plenum.